Method of controlling shrinkage of a sleeve wrap on a container

ABSTRACT

A method of forming a substantially encapsulating layer of a heat shrinkable polyolefin plastic on a glass container in which the neck, shoulder and body onto the bearing bottom surface of the container is covered. The body of the container is substantially greater in diameter compared with the neck. A cylindrical sleeve of the polyolefin is telescopically placed along the outer surface of the container and the two are conveyed together into a heating oven for shrinking the sleeve snugly over the container. Upon application of heat in the oven, the polyolefin initially softens and becomes limp such that the sleeve tends to fold over or upon shrinking creates wavy top margins on the shrunken covering. The invention includes controlled rotation of the bottle and sleeve in the oven to apply a centrifugal force to the limp plastic which remains erect and billowed outwardly to give the material time to react with the heat such that the sleeve material shrinks into overall even, snug contact about the contour of the container without folds and wrinkles. By way of example, heat shrinkable foam polyethylene sleeve material on the order of 4-5 inch diameter sleeve (bottle body diameter 4-5 inch and neck diameter 1-2 inch) and 14-15 mil thickness which is pre-oriented in machine direction (sleeve circumference) 60-80% and cross dimension 0-15% shrinks evenly and suitably onto the neck with good upper marginal control at a bottle rotation in the range of 150-300 RPM while immersed in the heat atmosphere of the oven at a production rate of approximately 100-250 BPM.

The present invention relates to manufacture of plastic shrink wrapcoverings on glass containers of the type disclosed in U.S. Pat. No.3,760,968; and particularly of the type disclosed on FIG. 14 of saidpatent.

BACKGROUND OF THE INVENTION

In the processing of glass bottles and the like for shrink applicationthereon of foam polyolefin sleeves, such as polyethylene, it isdesirable to shrink the sleeves onto the entire outer peripheral surfaceof the bottle to substantially encapsulate the surface area in theplastic sleeve, thus providing further cushioning of the glass surfaceand glass fragment retention capability should the bottom be broken.Bottles, and especially larger volume carbonated beverage bottles,include a relatively large diameter body that is for the most partcylindrical, a tapered or rounded shoulder portion that merges into arelatively small diameter neck, and a top "finish" or mouth portion overwhich there is applied a sealing closure after the bottle is filled. Byway of illustration, a typical bottle of this configuration may have amajor body diameter of 4-5 inches and a neck diameter of 1-2 inches.

In the use of certain pre-oriented and heat shrinkable foamed polyolefinmaterials, of which foamed polyethylene is a good example, the materialupon first stages of heating achieves a very limp and pliable condition.It has been found in the production of the full sleeve coverage on abottle, as mentioned, that the usual practices of heat immersion of thebottle and said polyolefin sleeves result in the upper section of thesleeve opposite the neck region of the bottle upon achieving the verylimp condition in the initial heating thereof will slump or fold overitself. After initial heating (the very limp stage), and a sufficientadditional time of heating, the material shrinks snugly onto the bottleand the segment that is folded over, it having also shrunken, produces adefective coating, i.e. offware, making the package unsalable.

In U.S. Pat. No. 3,843,316, there is disclosed a machine for theproduction of heat shrinkable plastic sleeves on articles, such asbottles, in which the bottles are conveyed by rotatable chuckssupporting the articles on spaced centers along a conveyor. Theapparatus of this patent applies the sleeve over the major or largerbody diameter segment of the bottle and into the sloping shoulder, andthe sleeve is a pre-oriented foam polystyrene. After the heat shrinkablepolystyrene sleeves are placed on the articles, the conveyor travelsthrough a heat applying device or oven, wherein the temperature ismaintained sufficiently to rapidly shrink the sleeves onto the articlesurface in a snug, surface conforming relationship. A rotary element ofthe chucks engages a stationary rail imparting rotation to the chucksand articles held thereby during their travel along the span of the ovenduring heat immersion of the articles and sleeves. The articles arerotated in the oven in response to travel therein for peripheraldistribution of heat during shrinking of the sleeve.

SUMMARY OF THE INVENTION

The present invention provides a method in which bottles or the like maybe wrapped with a limp or pliable heat shrinkable plastic, made frompolyolefin or polyolefin copolymer resins for substantially fullencapsulation of the exterior surface area of the bottle from adjacentthe closure finish portion to the bearing surface on the bottom wall.The method includes a controlled rotation of the bottle and the sleevetelescopically applied thereon about the central axis of the bottleduring heating such that the sleeve will shrink uniformly over theadjacent area of the bottle. The controlled bottle rotation diminisheswavy or folded tops of the sleeves being shrunken onto the bottle.

As was mentioned, the chuck on the conveyor carrying the bottle isrotatable about the common central axis of the two. As the conveyorenters the oven, the bottle and chuck are rotated such that therotational speed of the chuck will be regulated relative to line speed,shrink temperature, shrink dimension and properties of the material. Thecontrolled bottle rotation establishes a centrifugal force on the sleeveas the material achieves its limp condition during initial heating inthe oven, and the polyolefin sleeve remains substantially erect andbillowed while the material has time to heat further so that itprogressively shrinks beginning at the major body portion of the bottle.The shrinkage will progress upon further heating by the sleeve firstengaging the larger diameter portion of the bottle and progressivelysnugly shrinking over the remainder of the bottle surface until thesmallest diameter portion is snugly engaged by the contracting sleeve.In this manner, the defects of folding over of the sleeve or wavy topmargin of the shrunken sleeve is avoided. The centrifugal forcecomponent provided by controlled bottle rotation (150-200 RPM),maintains the material of the sleeve opposite the smaller diameter endportions of the bottle billowed out to give the resin time to react withthe heat supplied by the oven and shrink into place evenly and withoutwavy tops or wrinkles.

Other advantages and features of the invention will be more readilyapparent to those skilled in the art from the following detaileddescription of the drawings, which illustrate an apparatus for carryingout the method of the invention, on which:

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three-quarter side perspective view, in part schematic,showing the machinery and process for making a plastic wrapped bottle,and including apparatus for performing the method of this invention;

FIG. 2 is a detailed perspective view showing a bottle carried by thebottle conveyor of the apparatus through an oven for heating andshrinking the plastic sleeve thereon and employing the invention;

FIG. 3 is an end view, partly in section, of the bottle receiving thesleeve of heat shrinkable plastic from a mandrel device of the sleevemaking apparatus;

FIG. 4 is the first in a sequence of end views of the bottle and sleevein which the plastic sleeve is undergoing shrinking in an oven accordingto the method of the invention;

FIG. 5 is the second in a sequence of end views showing the bottle andsleeve at a later stage during the method;

FIG. 6 is the third in a sequence of end views showing the final plasticwrap on the bottle;

FIG. 7 is an end sectional elevational view of the apparatus shown onFIG. 2.

DESCRIPTION OF THE INVENTION

Shown on FIG. 1 is a machine for producing plastic sleeves on a turretmachine 10, assembling them telescopically over glass bottles 11 carriedby the conveyor 12 and shrinking them thereon in a heating apparatus 13.The glass bottles in the example of the present disclosure, after havinga shrunken plastic covering thereon, form a plastic wrapped container ofa type described and shown in the above mentioned U.S. Pat. No.3,760,968, as shown on FIG. 14 thereof.

Again referring to FIG. 1, in production of these containers, glassbottles 11 are picked up by the neck chucks 14 spaced along the endlessbottle conveyor 12 and carried through oven 13, indicated generally inphantom outline on FIG. 1. After receiving a sleeve of the plasticmaterial herein described, the conveyor path extends through the lengthof the oven chamber which is operated as a hot air chamber kept atelevated temperature by radiant heaters of sufficient magnitude forshrinking the plastic cylinderlike sleeve onto the bottle.

The plastic material used is a polyolefin or copolymers of olefins, forexample polyethylene, or laminates of polyolefins, e.g. polyethylenefoam layer and polyethylene film or a polystyrene foam and ethyleneacrylate film.

The plastic material of the polyolefin foam is made in sheet that ishighly oriented in the longitudinal dimension (M direction) of the webwhich is to become the circumference of the sleeve. There may be someorientation in the cross dimension of the web (T direction); however,this should be minimal in relation to the M direction orientation,because this T direction is ultimately the height dimension of thesleeve and it is desirable to control the top margin of the wrap leveland at a line along the bottle.

Examples of plastic sheet material that may be run in a web 15 arefoamed polyethylene on the order of 0.010-0.020 inch thickness andhighly oriented in the running (M) direction of web 15. M directionorientation for shrinkage should be at least 30% and on the order of60-80% is preferable. The cross (T) direction orientation should be lessthan 15% and in the range 0-15%.

In a more general way, the plastic sheet material may be a form of acontractible polyolefin or copolymer of olefins with vinyl esters, forexample, vinyl acetate, or with alpha, beta, monoethylenicallyunsaturated acids, such as ethyl acrylate or ethylene ethyl acrylate.The plastic is preferably in form of a foam sheet or a foam/filmlaminate sheet, but the principles of the invention will also work withnonfoam materials or solid sheet.

The general properties of the described materials in contraction(shrinking) is to achieve upon heating a first pliable, plastic state (avery limp condition) at which time the sheet material tends to sag,slump or fold, and this is followed after additional heating rathersuddenly by a shrinkage reaction.

In assembly of the plastic sleeve onto a bottle, the inner circumferenceof sleeve 16 is just slightly more than the exterior circumference ofthe bottle 11 at its largest portion, usually the body portion, so thatthe sleeve may be telescopically assembled over bottle 11 to the properelevation on the latter.

Referring again to FIG. 1, the web 15 of plastic sheet is mounted in aroll supply and unwound to a feed drum 18 which cuts the web intolengths for forming sleeves 16 (FIG. 3). The feed drum in turn feedseach of the cut lengths of the plastic to a mandrel 17 on the turretmachine 10. These components are more specifically shown and describedin U.S. Pat. No. 3,802,942.

Once the plastic is on the mandrel 17 and wound around it so that theends of the plastic overlap, a heated seal bar (not shown herein) of theturret machine 10 presses the overlapped plastic into a heat bonded,vertical seam securing the ends and making a substantially cylindricalsleeve 16. A stripper device 19 is shifted along mandrel 17 whichtransfers the plastic sleeve onto the overhead bottle 11.

Bottles 11 are loaded from an infeed conveyor 20 to the chucks 14 of theendless conveyor 12. The conveyor path is described at one end by thetwo end gears 21 and 22 on shaft 23 that is coaxial with the centershaft of turret machine 10, and at the other end by the two gears 24 and25 which rotate about shaft 26. The conveyor 12 is made up of chains 27and 28 reeved on the end gears 23, 24 and 22, 25, respectively. Thebottle chucks 14 pick up the bottles at the loading station over bottleinfeed conveyor 20 and are carried as parts of the assembly of theconveyor 12. Included on the conveyor are carriage brackets 29 carriedby the chain 27, 28 along which the cylinder assembly 30 is slidablymounted. The height elevation of the chucks 14 in the conveyor path iscontrolled by a cam roller 31 which operates on the upper cam track 32.The opening and closing movement of the jaws of chuck 14 are controlledby cam roller 33 running in the cam track 34. Thusly, the bottles 11 arepicked up in succession by the bottle conveyor and carried in the path Aindicated by the line and arrows on FIG. 1. This path includes argistration of each bottle with an underlying sleeve of the plasticmaterial which is pushed upwardly by stripper 19 over the bottle. Thebottle with sleeve thereon next proceeds to oven 13 to be heated andprocessed in accordance with the present invention. As the sleeve 16reaches its assembled height on bottle 11, the conveyor path A extendsalong a water cooled sleeve support bar 35 which extends from adjacentthe mandrel path on turret machine 10 well into the oven 13. Thestructural details of support bar 35 are disclosed in copendingapplication Ser. No. 658,631 filed Feb. 17, 1976, owned by a commonassignee with the present application. The support bar 35 will assurethe elevation of the sleeve on the bottle at least until such time asshrinkage of a degree similar to that illustrated on FIG. 4 is achievedin the oven 13. In this state, the contractible sleeve has shrunken toengage at least an annular portion of the major body (large diameter) ofbottle 11 to hold the sleeve in place during the balance of the process.

The bottle 11, illustrated on FIGS. 2-7, is typical of carbonatedbeverage bottles in use today. Referring to the bottle on FIG. 3, whichis the same as shown on the other Figures, it includes a major diameterbody portion 11a, a rounded shoulder portion 11b at the upper end of thebody which merges into the minor diameter neck portion 11c. The neck 11cmay, as is illustrated, include a carrying ring 11d molded in the glass.Above ring 11d the neck merges into the bottle finish 11e which includesan annular rim 11f at the top of the bottle defining the opening ormouth for filling and pouring. At the other end of bottle 11, the sidewall of body 11a merges into the bottom wall 11g at the corner radius orheel portion 11h. By the term "major diameter" it is meant the largercross dimension of the bottle; and, by the term "minor diameter" it ismeant a substantially lesser cross dimension of the bottle than saidmajor diameter. As an example, the bottle may have a body 11a of adiameter on the order of 4-5 inches, a major diameter, and the neck 11cbelow the ring 11d is a minor diameter on the order of 1-2 inches. Thesleeve 16 is placed to an assembled position, as shown on FIG. 3,encircling the body and neck portions of the bottle so that the top edge16a of the sleeve is at least within about 1/2 inch of the finish 11e.In the example shown, this locates the edge 16a at about the elevationof the lower margin of ring 11d of the bottle.

After the bottle and sleeve enter oven 13 (FIG. 1), the chuck ispositively driven by a belt or chain drive means controlled to impartrotation to the bottle sufficient such that centrifugal forces bearingon the sleeve in the portions encircling the lesser or minor diameterportions of the bottle of sufficient magnitude to hold the sleeve erectas the polyolefin is heated and becomes soft and pliable. As the sleevematerial reaches its shrink temperature, the initial shrinkage shouldoccur at the body portion 11a of the bottle. The sleeve will be shrunkeninto contact with the wall of the body of bottle 11 in the middle areasfirst. This is best accomplished by having the glass bottle preheated toelevated temperature (100°-250° F) and by applying the oven heat so thatit is concentrated first around the body portion and next toward the topand bottom edges of the sleeve, i.e. edges 16a and 16b.

The rotation of the bottle while traveling in the oven is performed bythe apparatus to be described. Referring to FIG. 2, each bottle chuck 14has its upper cylinder 30 slidably mounted in the slides 29a of bracket29 for vertical movement of the cylinder under control of the cam roller33 and cam track 34. The bracket 29 is fastened to upper and lowercarriage chains 27 and 28 and includes a roller 36 running in the track37 extending around the endless path on the machine.

As seen on FIG. 7, track 37 is fastened to the structural framework 45of the machine. So that the path of carriage 29 will not wobble, theupper and lower C-shaped bosses 46 for connecting the carriage 29 to thechains 27 and 28 each also include a stub shaft 47 and rotatable roller48. Each roller 48 runs in a similar guide track 49 fastened to thestationary main frame 45. Track 49 follows the path of the chain atleast in the portions of the endless path wherein the process is beingperformed. This structure adds stability to the bottle carriagemechanism. Accordingly, the carriage bracket 29 travels the endless pathcorresponding to that of chains 27 and 28 and is pulled by the chainsconnected thereto. The cylinder 30 of each chuck assembly is manipulatedvertically along bracket 29 by the cam roller 33, cam 34 for placing thechuck 14 at the proper elevation in the various process steps ofhandling of the bottle.

As seen on FIG. 7, the chuck jaws 14 are pivoted open and closed about abottle finish 11e by a yoked piston 38 carrying the cam roller 31. Asmentioned before, roller 31 engages a cam 32 controlling the open orclose position of the chuck jaws 14. The piston 38 slides vertically incylinder 30 and is limited by a pin 39 extending through the wall ofcylinder 30. The underside of piston 38 engages a chuck rod 40 whichextends axially of cylinder 30 and connects to the chuck support collar41. Collar 41 is pivotally supported on the end of a hollow shaft 42 andthe chuck rod 40 extends through the hollow shaft 42. Shaft 42 ismounted in bearings in cylinder 30 such that the shaft and chuck supportcollar 41 plus the chuck jaws 14 are rotatable. Chuck rod 40 is springloaded at the underside of piston 38 such that rod 40 is normallyextended upwardly riding the cam roller 31 in contact with the cam 32.

The chuck support collar 41 includes a rotary driven element 43 which,in the illustration on the drawings, is a pulley driven by the poweredendless member 44 in mesh or driving contact therewith. The member 44,in the illustrated example herein, is a V-belt. The element 43 andmember 44 could take the form of a sprocket and link chain, such as abicycle-type chain. The belt member 44 is driven in a manner to bepresently described such that the pulley 43 and the chuck support collar41 and chuck jaws 14 attached thereto are driven in a controlled speedof rotation during the portion of travel of the sleeve and bottle in theoven wherein the sleeve is undergoing shrinkage.

Referring to FIG. 1, the belt 44 is reeved about an end pulley 50rotatably mounted on the machine frame and about the drive pulley 51 onthe power transmission unit 52. Along the active span of belt 44 thereare several freely rotatable back-up rollers 53 which extend over thespan of travel for the chucks while in the oven. The back-up rollers 53may be located on about a 6-inch spacing of their centers along thisspan of the belt. The back-up rollers 53 are spring loaded against thebelt, such as is illustrated on FIG. 2, which hold the belt into thepath of the pulley 43 on each of the chucks and assure drivingengagement of the belt 44 with the pulleys 43. An end idler pulley 54guides the belt over the drive pulley 51. An adjustable take-up pulley55 is rotatably mounted on an adjustable means (not shown) on the backside of the belt run to maintain the belt in a taut condition.

Transmission unit 52 is a reversible, variable speed type operated by anelectric motor 56 connected to the transmission input sprocket 57 by achain drive 58. Transmission 52 is preferably operated to run the beltin a direction counter to the direction of travel of the chucks throughoven 13, that is, on FIG. 1 in a clockwise direction (the carriagechains 27, 28 are being driven in a counter clockwise direction). Inthis fashion, the line speed of the chucks through the oven will beadditive with the speed of belt 44 and their sum will provide therotation to the chucks in the oven for the purposes of the invention.The running speed of the belt 44 may be varied through the motor andtransmission to achieve the desired RPM of the chucks as they travelthrough the oven.

The path of belt 44 will be controlled by the series of back-up rollers53 such that the belt 44 will engage each of the pulleys 43approximately at the time the bottle carried by that chuck 14 enters thefront end of oven 13. At this point, the elevation of the chuckcylinders 30 is established by cam track 34 such that each of thepulleys 43 will mesh with belt 44. The prescribed rotational speed ofthe chuck and bottle determined by line speed of conveyor 12 and runningspeed of belt 44, will be achieved in the forward end of the ovenatmosphere for size of bottle and dimensions and composition of thecylindrical form of sleeve thereon. As the bottle passes to and in theoven, the lower edge 16b of the sleeve will be guided on water cooledbar 35 so as to maintain proper height elevation of the sleeve on thebottle.

Referring now to the sequence of FIGS. 3-6, the method of shrinking thepolyolefin type of sleeve on the bottle is illustrated. As seen on FIG.3, the sleeve is moved telescopically along the central axis of bottle11 by the UP motion of stripper element 19 so as to transfer thecylindrical sleeve 16 from the mandrel 17 and into the assembledposition. The bottle and sleeve then move into the oven and the sleeveis exposed to the heating needed for shrinking. In the use ofpolyethylene sleeves, the operating temperature of the oven is in therange 600°-900° F under production conditions of approximately 100°-250°BPM.

In the oven 13, the heat is supplied by hot air or infra-red burners anddirected onto the bottle as it passes along the oven in a patternindicated on FIGS. 4 and 5. The heat pattern is indicated thereon by theencircled H legend plus the arrows. The forward section of the ovendirects the heat as shown on FIG. 4 toward the body section 11a of thebottle. After the polyolefin material is being elevated in temperatureto a degree necessary for shrinking, the sleeve becomes limp. However,by this time the bottle and sleeve are brought up to a rotational speedto apply centrifugal force to the upper and lower segments 16c and 16d,respectively, of the sleeve material which force maintains the sleeveerect and these unsupported end segments 16c and 16d are billowedoutwardly as shown on FIG. 3. In the example given, such as a glassbottle preheated to 110°-125° F having a body diameter at 11a of 4-5inches and a neck diameter at 11c of 1-2 inches, and using a foamedpolyethylene matrix with solid polyethylene exterior skin of 1-3 milsthickness, the composite thickness being 14-15 mils, and wherein thecircumferential (M.D.) shrink factor or orientation is 60-80% and theheight (C.D.) shrink factor is 0-15%, the bottle rotation of 250-275 RPMproduces a centrifugal force sufficient to achieve the billowed effectof the sleeve segments 16c and 16d while the intermediate segment isshrinking onto the bottle. As the bottle passes into the next adjacentpart of oven 13, the heat is applied or directed onto the bottle inaccordance with the pattern shown on FIG. 5 (represented by theencircled H legend and arrows), wherein heat is now concentrated againstthe upper segment 16c and the lower segment 16d of the sleeve. Rotationof the bottle continues while these segments achieve temperature forshrinking and undergo the contraction until the material thereof shrinkssnugly along the wall of the bottle at the neck section 11c and over theheel section 11h and onto the annular bearing section of the bottom wall11g.

After the sleeve has finally achieved the full shrunken condition, theproduct of the bottle and sleeve is shown on FIG. 6. The top marginaledge 16a of the sleeve has now snugly encircled the neck just under thering 11d; whereas, the bottom marginal edge 16b has curled under thebottom of the bottle and encircled the heel radius portion 11h. The topand bottom margins of the wrap are free of wavy and wrinkled appearance.The sleeve wrapped bottle (indicated as F on FIGS. 1 and 6) has arelatively tough, cushioned covering on the exterior surface that is ina snug fitting conforming engagement substantially encapsulating thebottle. Only the carrying ring 11d, finish portion 11e and central areaof bottom 11g are left uncovered. The need for exposure of thesesurfaces in the use of the bottle should be readily apparent.

At the point of production illustrated on FIG. 6, the wrapped bottle Fexits the oven and rotation of the chuck and bottle ceases by adisengagement of the belt 44 with pulley 43, which will occur naturallyby the diverging path of belt 44 between the last back-up roller 53 andthe guide roller 54 from engaging the pulley 43 of the chucks travelingalong the path prescribed by the carriage chains 27 and 28. As shownschematically by the line and arrow path on FIG. 1, each chuck cylinder30 lowers the chuck jaws 14 by sliding downwardly along the carriagebracket under control of roller 33 which is following the dip in cam 34.The cam 34 lowers the bottle such that it is nearly engaging the exitconveyor 59. At this time, the roller 31 controlling the opening-closingmovement of chuck jaws 14 encounters the sharp dip in cam 32 opening thejaws and releasing the bottle product F to the exit conveyor 59.Thereafter, the chuck mechanism and carriage conveyor repeat the cycleupon passing the loading point over the bottle infeed conveyor 20.

Referring again to FIG. 2, the apparatus illustrates the travel of thebottle in the forward section of oven 13 wherein the heat is beingdirected predominantly toward the body section 11a of the bottle. Theone half portion of the oven 13 shown represents the exhaust half side13b of the oven in which the central louver controlled slots 60 controlthe flow of heat across the oven into the intermediate zone of thebottle and along the path of the bottle thereat. In this section thecentral louvers of slots 60 control major flow of the heated air acrossthe intermediate region of the bottle path. By the same principle, thenext stages of the oven will include top and bottom bottle zone exhaustslots 61 that direct the heated air principally toward heating the topand bottom regions of the bottle in its path through the aft section ofthe oven. Together these serially arranged oven sections apply the heatfor shrinking the sleeve in accordance with the patterns described andillustrated on FIGS. 4 and 5.

As shown on FIG. 7, the bottle is moving toward the observer and theheating is applied in this cross-sectional view from the left hand onehalf of the heating apparatus 13a housing burners (not shown) across thetop and bottom zonesover the upper and lower billowed portions 16c and16d of the sleeve and into the exhaust one half of the oven 13b, justdescribed.

As mentioned earlier, the sleeves may be made from sheet stock of apre-oriented polyolefin or copolymers of olefins, for examplepolyethylene of either high density or low density grade, or laminatesof polyolefins, e.g. polyethylene foam layer and polyethylene film. Theproperty of these materials in contraction (heat shrinking) is a firstpliable or limp state during which the sheet of the sleeve tends to sag,slump or fold easily, followed by a shrinkage reaction. This inventiondeals effectively with the propensity of the material of the typedescribed to slump or sag in the initial stages of heating by improvingor making it feasible for the material of the sleeve to shrink evenlywhen it reaches a temperature to do so and without wrinkles, such thatthe bottle is covered up to the finish end, along the neck and on thebody to the bottom annular bearing surface.

The preheating of the glass bottle, indicated herein as beneficial inthe process, is accomplished just prior to the telescopic assembly ofthe cylindrical sleeves thereover. This may be done in an oven placedalong the path of the conveyor after the bottle loading station, or hotbottles from the manufacturing line producing the bottles may bepresented to the loading station at proper elevted temperature. The hotglass or heat in the bottle glass is especially beneficial in theshrinkage of the foam sheet materials in sleeve form over the bottlesurface.

Having described a preferred embodiment of the invention and illustratedin connection therewith a preferred form of apparatus for carrying outthe method of the invention, it should be understood that furthermodifications may be resorted to without departing from the spirit andscope of the appended claims.

What is claimed is:
 1. The method of shrinking a heat shrinkable plasticsleeve form onto a container, said container having a major diameterbody portion and one or more substantially smaller portions of minordiameter including a finish portion defining a mouth opening to thecontainer, comprising the steps ofproviding containers in uprightposition at a loading station, grasping the containers by their upperfinish portions at the loading station by a chuck device carried on aconveyor, moving the conveyor past a source of sleeves slightly largerin size than the major diameter of the container and made of apolyolefin plastic material that is pre-oriented circumferentially atleast for 30% or greater shrinkage upon heating, assembling a sleeve ofsaid material axially over the container, the sleeve being of a heightdimension so as to extend from adjacent the finish portion of thecontainer to adjacent the other end thereof, conveying the container andsleeve in an oven maintained at elevated temperature sufficient toshrink said material of the sleeve onto the container, rotating thecontainer and sleeve about their central axis while in the oven at arate of rotation that is sufficient to generate a centrifugal forcecomponent on the sleeve so as to maintain the plastic of the sleeveoverlying said minor diameter portions of the container erect andbillowed out for a time while the portion of said sleeve adjacent themajor diameter portion of the container is shrunken thereon, andthereafter shrinking the balance of the sleeve onto the adjacent minordiameter portions of the rotating container so as to wrap the containerbelow the finish portion thereof with a snug fitting conforming coveringof the plastic on the exterior of the container.
 2. The method of claim1, wherein the container is rotated about its axis in the range of150-300 RPM.
 3. The method of claim 2, wherein the container is a glassbottle.
 4. The method of claim 2, wherein the plastic material comprisesa heat contractible, pre-oriented sheet of plastic selected from thegroup consisting of a polyolefin and copolymer of olefins with vinylesters.
 5. The method of claim 4, wherein the plastic material is apolyethylene.
 6. The method of claim 5, wherein the polyethylenecomprises a foamed polyethylene that is in the range of 0.010-0.020inches in thickness.
 7. The method of claim 6, wherein the polyethylenefoam material includes a skin of polyethylene film thereon that is inthe range of 0.001-0.003 inches in thickness.
 8. The method of claim 3,wherein the glass bottle is at an elevated temperature in the range of100°-250° F at the time the sleeve of said plastic material is appliedover the bottle exterior surface.
 9. The method of shrinking a plasticsleeve-like form of heat shrinkable material onto a containercomprisingproviding a container having a sleeve of the plastic materialdisposed axially thereon, the height of the sleeve correspondingsubstantially with the exterior height of the container such that thesleeve, upon shrinkage, will cover substantially the exterior surface ofthe container, heating the sleeve on the container in a device atelevated temperature sufficient for shrinking the sleeve over thebottle, rotating the container and sleeve during said heating at a rateof rotation to create a centrifugal force on the sleeve tending to holdthe sleeve away from the container and in an erect sleeve form, saidheating step comprising first heating the sleeve at the major body ofthe container during said rotation so as to shrink that portion of thesleeve snugly over said major portion, and thereafter heating thebalance of the sleeve so as to shrink the other portions snugly on thecontainer during said rotation, providing a shrunken plastic coveringthereon extending over substantially the exterior surface area thereof.10. The method of wrapping the surface of a glass container with a heatshrinkable plastic comprisingproviding a container in vertical uprightposition with a sleeve telescopically assembled loosely along theexterior of the container and extending over substantially the axialdimension thereof, said sleeve being made from a heat shrinkable plasticselected from the group consisting of polyolefins and copolymers ofolefins with vinyl esters that is pre-oriented in the circumferencethereof at least 30% and in the height dimension 0-15%, heating saidsleeve on the container, whereupon the plastic becomes limp, rotatingthe container and sleeve about the central axis of the container duringsaid heating at a speed providing a centrifugal force on the limpplastic sleeve to hold it erect and prevent portions thereof unsupportedby the container from folding or slumping, and shrinking the sleevesnugly over the surface of the container during said rotation providinga wrap of said plastic thereon over its exterior surface characterizedby even edge margins and being void of wrinkles.
 11. The method ofshrinking a heat shrinkable sleeve of plastic material over the exteriorsurface of a bottle having a body portion of major cross dimension and aneck of minor cross dimension comprisingplacing a sleeve of a heatshrinkable plastic near ambient temperature on the bottle in verticalupright position, said sleeve having an inside dimension slightly largerthan said major dimension of the bottle and extending substantially overthe height of the bottle, said plastic being pre-oriented predominantlyin the circumferential dimension of the sleeve, heating the sleeve to anelevated temperature sufficient for shrinking it on the bottle duringwhich the plastic becomes limp and pliable preceding shrinkage, androtating the sleeve with the bottle during said heating about thecentral axis of the bottle and while the plastic of said sleeveincreases in temperature to shrinkage thereof, said rotational speedbeing controlled to create centrifugal forces on said plastic sleevemaintaining the latter erect and along the bottle surface whileshrinking snugly to the contour of the bottle surface, thereby avoidingirregularities in the plastic wrap covering thereon.
 12. The method ofclaim 11, wherein the heat shrinkable plastic comprises a materialselected from the group consisting of polyolefins and copolymers ofolefins with vinyl esters.
 13. The method of claim 12, wherein saidrotational speed of the bottle is in the range of 150-300 RPM.
 14. Themethod of claim 13, wherein the material comprises polyethylene.
 15. Themethod of claim 14, wherein the rotational speed of the bottle is in therange of 250-275 RPM.
 16. The method of claim 15, wherein saidpolyethylene sleeve is on the order of 0.010-0.020 inches in thicknessand is comprised of a foamed polyethylene.
 17. The method of claim 16,wherein said polyethylene sleeve includes a film surface layer ofpolyethylene on the order of 0.001-0.003 inches in thickness.
 18. Themethod of claim 11, wherein the bottle is at elevated temperature in therange of 100°-250° F at the time of placing said plastic sleeve thereon.